This invention is directed to connectors for tightly joining together extruded lengths of aluminum channel or the like. Within this field it is well known to encompass a glass or picture area within a frame whose channel members are held together by corner connectors which are fastened to the channel by devices acting at right angles to the area or the channel.
Examples of threaded devices which act in a direction normal to the framed area are the Canadian Pat. Nos. 535,351 (1958) to Secord, and 1,035,952 (1978) to Nielsen; and U.S. Pat. No. 3,018,861 (1962) to Somville, all of which employ screws driven against the base of the rail. In Canadian Pat. No. 925,292 (1973) to Vihma a channel-rail is gripped between a nut and bolt; other patents showing gripping through threaded members are U.S. Pat. Nos. 2,654,451 (1953) to Schmidgall, 2,816,632 (1957) to Nardulli, and 2,947,391 (1960) to Wayne. Another method is the tie-bar approach found in Canadian Pat. No. 826,550 (1969) to Myatt where force along the rail is applied by mean of cam surfaces engaged at right angles to the rail.
A further approach for joining lengths of channel is to insert longitudinal parallel gripping bars within specially formed channels, and separate these by screws or cams to clamp, as seen in U.S. Pat. No. 2,790,259 (1957) to Havens; such an approach cannot be used to join corners together, only straight lengths.
The disadvantages of the so-called threaded fastenings heretofore discussed are that set-screws, jack-screws, bolts and nuts are small end easily lost or misplaced. Further, being basically devices which apply force at right angles to the frame and its members, these screw devices do not apply a force component longitudinally of the channels in a direction to drive them into a tightly fitting joint.
Additionally, many channel cross-sectional configurations require special fasteners, and vice versa, tending to reduce applicability.